Controlling semiconductor film thickness

ABSTRACT

In certain embodiments, a method for processing a semiconductor substrate includes depositing a resin film on a substrate that has microfabricated structures defining recesses. The resin film fills the recesses and covers the microfabricated structures. The method includes performing, using a photoacid generator (PAG)-based process, a localized removal of the resin film to remove the resin film to respective first depths in the recesses, at least two depths of the respective first depths being different depths. The method includes repeatedly performing, using a thermal acid generator (TAG)-based process and until a predetermined condition is met, a uniform removal of a remaining portion of the resin film to remove a substantially uniform depth of the resin film in the recesses.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.63/073,047, filed on Sep. 1, 2020, which is incorporated by reference.

TECHNICAL FIELD

This disclosure relates generally to semiconductor fabrication, and, incertain embodiments, to controlling semiconductor film thickness.

BACKGROUND

Constructing electrical circuits involves depositing numerous layeredmaterials across various features or structures, as well as patterning,etch, and fill processes. As design innovation for next generationtransistors moves to smaller dimensions and vertical architectures,desire for technology that precisely controls film thickness within adie and across a wafer increases. Etch processes can be timed to removea portion of a film without an endpoint; however, such processes havepoor locational control and high variability.

SUMMARY

In certain embodiments, a method for processing a semiconductorsubstrate includes receiving a substrate having microfabricatedstructures defining recesses and depositing a resin film on thesubstrate. The resin film fills the recesses, covers the microfabricatedstructures, and is initially resistant to development by a solvent. Themethod includes depositing a first overcoat film on the substrate. Thefirst overcoat film contains a first agent-generating ingredient thatgenerates, in response to actinic radiation, a first solubility-changingagent. The method includes exposing the first overcoat film to firstsufficient actinic radiation to generate the first solubility-changingagent within the first overcoat film. The method includes diffusing thefirst solubility-changing agent a first predetermined depth into theresin film causing a first portion of the resin film to become solubleto the first solvent, and developing the first overcoat film and thefirst portion of the resin film using the first solvent. The methodincludes depositing a second overcoat film on the substrate. The secondovercoat film contains the first agent-generating ingredient thatgenerates, in response to actinic radiation, the firstsolubility-changing agent. The method includes exposing the secondovercoat film to second sufficient actinic radiation to generate thefirst solubility-changing agent within the second overcoat film. Themethod includes diffusing the first solubility-changing agent a secondpredetermined depth into the resin film causing a second portion of theresin film to become soluble to the first solvent, and developing thesecond overcoat film and the second portion of the resin film using thefirst solvent resulting in the resin film being recessed respectivefirst combined depths in the recesses.

In certain embodiments, a method for processing a semiconductorsubstrate includes receiving a substrate having microfabricatedstructures defining recesses and depositing a resin film on thesubstrate. The resin film fills the recesses, covers the microfabricatedstructures, and is initially resistant to development by a firstsolvent. The method includes depositing a first overcoat film on thesubstrate. The first overcoat film contains a first agent-generatingingredient that generates, in response to actinic radiation, a firstsolubility-changing agent. The method includes exposing the firstovercoat film to sufficient actinic radiation to generate the firstsolubility-changing agent within the first overcoat film. The methodincludes diffusing the first solubility-changing agent a firstpredetermined depth into the resin film causing a first portion of theresin film to become soluble to the first solvent, and developing thefirst portion of the resin film using the first solvent. The methodincludes depositing a second overcoat film on the substrate. The secondovercoat film contains a second agent-generating ingredient thatgenerates, in response to heating of the substrate, a secondsolubility-changing agent. The method includes baking the substratesufficiently to generate the second solubility-changing agent within thesecond overcoat film and diffuse the second solubility-changing agent asecond predetermined depth into the resin film causing a second portionof the resin film to become soluble to the first solvent. The methodincludes developing the second portion of the resin film using the firstsolvent resulting in the resin film being recessed respective combineddepths in the recesses.

In certain embodiments, a method for processing a semiconductorsubstrate includes depositing a resin film on a substrate that hasmicrofabricated structures defining recesses. The resin film fills therecesses and covers the microfabricated structures. The method includesperforming, using a photoacid generator (PAG)-based process, a localizedremoval of the resin film to remove the resin film to respective firstdepths in the recesses, at least two depths of the respective firstdepths being different depths. The method includes repeatedlyperforming, using a thermal acid generator (TAG)-based process and untila predetermined condition is met, a uniform removal of a remainingportion of the resin film to remove a substantially uniform depth of theresin film in the recesses.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this disclosure, and the advantagesthereof, reference is now made to the following descriptions taken inconjunction with the accompanying drawings, in which:

FIGS. 1A-1J illustrate cross-sectional and plan views of an examplesemiconductor substrate during an example process for processing thesubstrate;

FIGS. 2A-2I illustrate cross-sectional and plan views of an examplesubstrate during an example process for processing the substrate;

FIG. 3 illustrates example effects of varying depths of diffusion of asolubility-changing agent into a fill material;

FIGS. 4A-4H illustrate cross-sectional views of example substrateportions having pre-patterned features during example process forprocessing the substrate portions;

FIGS. 5A-5C illustrate cross-sectional views of example substrateportions having pre-patterned features during portions of exampleprocess for processing the substrate portions;

FIG. 6 illustrates an example method for processing a semiconductorsubstrate;

FIG. 7 illustrates an example method for processing a semiconductorsubstrate;

FIG. 8 illustrates an example method for processing a semiconductorsubstrate;

FIGS. 9A-9C illustrate example PAGs and TAGs that may be used inovercoat films;

FIGS. 10A-10B illustrate example modification of the solubility ofovercoat films and/or a fill material;

FIG. 11 illustrates examples of stacked transistor architectures thatmay benefit from precise film height control to selectively grow n-typeand p-type silicon-germanium (SiGe); and

FIGS. 12A-12B illustrate that a step in a self-aligned block (SAB)process flow may benefit from a partial recess of a specific film, suchas a spin-on carbon.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Throughout the deposition, patterning, and removal processes associatedwith forming a semiconductor device, it may be desirable to control theheight of a deposited film for various reasons. For example, it may bedesirable to remove a portion of a deposited film (e.g., in a trench) toachieve a certain height of that deposited film within the trench.Conventional removal processes, such as timed wet or dry etch processes,for removing portions of a deposited layer are often difficult tocontrol and suffer other problems, such as planarization problems. Theseproblems become even more prevalent as feature sizes continue to shrinkor vary across the surface of a semiconductor wafer being processed.

Embodiments of this disclosure provide techniques to control filmthickness for a semiconductor substrate. The substrate may havepre-patterned features that include, for example, structures definingrecesses. The film being controlled may be a fill material, such as apolymer resin, deposited over the pre-patterned features, filling therecesses and covering the structures. Across a semiconductor wafer thatincludes the substrate, precisely and repeatably reducing the fillmaterial to particular target heights (thicknesses) within recesses maybe desired, and those target heights might vary from among recesses.Certain embodiments accomplish this film thickness control without usingan etch stop layer or other timed etch process used with conventionaletch techniques in which control of film height is desired.

The fill material may be initially resistant to removal (e.g.,development) by a solvent (e.g., developer) to be used in removing aportion of the fill material. Certain embodiments use a cyclic processthat includes depositing an overcoat film containing an agent-generatorthat, in response to a stimulus, generates an agent in the overcoatfilm. The agent is then diffused into the fill material to apredetermined depth, causing a portion of the fill material to becomede-protected (removable/developable) relative to the solvent. Theovercoat film and the de-protected portion of the fill material are thenremoved using the solvent. This process can be repeated until the fillmaterial in the recesses reaches one or more corresponding targetheights.

Certain embodiments use a PAG-based process to reduce at least a portionof a height of a resin film in recesses of a substrate. For example, theagent-generator in the overcoat film may be a photo-activated agentgenerator (e.g., a PAG) that is activated in response to actinicradiation. This PAG-based process may be repeated a suitable number oftimes until target films heights (e.g., within recesses) are achieved.

Certain embodiments use a TAG-based process to reduce at least a portionof a height of a resin film in recesses of a substrate. For example, theagent-generator in the overcoat film may be a thermally-activated agentgenerator (e.g., a TAG) that is activated in response to heat. ThisTAG-based process may be repeated a suitable number of times untiltarget films heights (e.g., within recesses) are achieved.

Certain embodiments combine one or more iterations of the PAG-basedprocess to establish height variations in the resin film with one ormore iterations of the TAG-based process to uniformly further reduce thefilm height thickness until the target film heights (e.g., withinrecesses) are achieved.

That is, embodiments provide modulation of film thickness and profile bylocation across a wafer by generation and diffusion of acid from anovercoat into an acid-de-protectable resin, followed by development.Depth of the acid de-protection into the resin film may be defined bythe amount of acid produced in, and diffused from, the overlyingovercoat. Locational height control may be achieved using photoacidand/or thermal-acid generator containing overcoats. Embodiments can beused with backside overlay control techniques as well as location-basedcritical dimension optimizer platforms for front side treatment.

Certain embodiments also provide improved planarity. For example,certain conventional etch techniques introduce or exacerbateplanarization problems, particularly as pitches between structures of asubstrate, or the widths of those structures, vary. Certain embodimentsof this disclosure are able to control removal of a fill material totarget heights with little to no effects introduced by the varyingtopography of a substrate.

FIGS. 1A-1J illustrate cross-sectional and plan views of an examplesemiconductor substrate 100 during an example process 102 for processingsubstrate 100, according to certain embodiments. Process 102 includesstages 104 a-104 j, though process 102 may include more or fewer stagesif appropriate. Substrate 100 may be part of a larger semiconductordevice, such as part of a larger semiconductor wafer. In certainembodiments, process 102 includes repeatedly performing a PAG-basedprocess to remove a fill material from a recess of substrate 100 untilthe fill material is a predetermined height within the recess.

As shown in FIG. 1A at stage 104 a, substrate 100 includes base portion106 and microfabricated structures 108 formed on base portion 106.Structures 108 define recesses 110. This disclosure contemplatesstructures 108 being patterned into any suitable features. For example,although this disclosure primarily describes “recesses,” other suitablefeatures might be formed in or on a semiconductor substrate, including(whether or not considered “recesses”) lines, holes, trenches, vias,and/or other suitable structures, using embodiments of this disclosure.Structures 108 and recesses 110 may be formed using conventionallithography processes and/or other suitable deposition and etchprocesses. Base portion 106 and structures 108 may include the same ordifferent materials (or combinations of materials), as appropriate.

Substrate 100 generically refers to a workpiece being processed inaccordance with embodiments of this disclosure. Substrate 100 mayinclude any material portion or structure of a device, particularly asemiconductor or other electronics device, and may, for example, be abase substrate structure, such as a semiconductor wafer, reticle, or alayer on or overlying a base substrate structure such as a thin film.Thus, substrate 100 is not limited to any particular base structure,underlying layer or overlying layer, patterned or un-patterned, butrather, may include any such layer or base structure, and anycombination of layers and/or base structures. Substrate 100 may be abulk substrate such as a bulk silicon substrate, a silicon on insulatorsubstrate, or various other semiconductor substrates.

Structures 108 have respective top surfaces 112, and recess 110 hasbottom surface 113. In certain embodiments, structures 108 and recesses110 differ in height relative to each other. For example, in certainembodiments, recesses have a height 114 (in a z-direction from a bottomof base portion 106 to bottom surface 113 of recess 110), and structures108 have a second height 116 (from a bottom of base portion 106 to topsurfaces 112 of structures 108 in the z-direction). In certainembodiments, the height difference of structures 108 and recess 110relative to each other may be between 10 nm and 100 nm (e.g., greaterthan 50 nm). In other embodiments, the height difference may be greaterthan 5 microns, in case of a deep opening/trench for example. Structures108 are separated by a gap (e.g., defined by recess 110), which may haveany suitable width 118 for a given application.

As shown in FIG. 1B at stage 104 b, a fill material 120 has beendeposited on substrate 100. Fill material 120 may be deposited in anysuitable manner. For example, fill material 120 may be deposited usingspin-on deposition (or spin-coating), spray-coating, roll-coating,chemical vapor deposition (CVD), or any other suitable depositiontechnique. Fill material 120 fills recess 110 and covers structures 108.In subsequent photolithography steps, it may be desirable to recess, viaphotolithographic development techniques, fill material 120 into recess110, such that fill material 120 has a particular height within recess110.

In certain embodiments, fill material 120 is a resin film, such as apolymer resin. Fill material 120 may have a photo-de-protectableproperty and, as deposited, may be resistant to being dissolved by agiven solvent (which also may be referred to as a developer). As will bedescribed in later stages, after exposure to a particular acid, however,the fill material 120 can experience a solubility change after which thefill material 120 (or portions thereof) is no longer protected from thesolvent and will dissolve in the solvent. For example, in certainembodiments, fill material 120 is an acid de-protectable polymer, and aportion of the polymer will react with a certain species (e.g., an acid)to decompose in order to shift solubility of fill material 120 such thatfill material 120 will dissolve or otherwise wash away if de-protectedin a particular way. As particular examples, fill material 120 may be acopolymer or terpolymer composed of multiple types of monomers with atleast one of the monomers able to decompose in the presence of a strongacid to make a more polar group like a carboxylic acid terminal group,so that fill material 120 will be more soluble in an aqueous medium. Asa particular example, fill material 120 may include multiple monomertypes including an acid sensitive monomer such as tert-butyl acrylate ormethyl adamantyl methacrylate.

In certain embodiments, fill material 120 includes a photosensitivematerial such as a positive, negative, or a hybrid toned photoresist. Inone example, fill material 120 includes phenol formaldehyde resin or adiazo-naphthoquinone based resin. In certain embodiments, fill material120 may include a chemically amplified resist. In other embodiments,fill material 120 may include a non-chemically amplified resistmaterial, such as PolyMethyl MethAcrylate (PMMA) or HydrogeneSilsesQuioxance (HSQ).

It may be desirable to remove a portion of fill material 120, includingwithin recess 110, such that fill material has a predetermined targetheight 121 within recess 110. In this example, target height 121 isshown to be measured from bottom surface 113 of recess 110; however, thetarget height of fill material 120 within recess 110 may be measuredfrom any suitable location, such as the bottom of base portion 106.Target height 121 also may be considered a target thickness of fillmaterial 120. Fill material 120 is initially resistant to development byone or more solvents that will be used in a subsequent process to removeportions of fill material 120.

As shown in FIG. 1C at stage 104 c, an overcoat film 122 has beendeposited on substrate 100. Overcoat film 122 may be deposited in anysuitable manner, including spin-on deposition (or spin-coating),spray-coating, roll-coating, CVD, or any other suitable depositiontechnique. Overcoat film 122 contains a photo-activated agent generatorthat generates, in response to actinic radiation, a solubility-changingagent for changing the solubility of another material (e.g., thematerial of overcoat film 122 and/or fill material 120) to be soluble inone or more solvents to be used in a subsequent removal process. Incertain embodiments, the photo-activated agent generator is a PAG andthe solubility-changing agent is acid.

Aside the photo-activated agent generator, overcoat film 122 might ormight not include the same material as or a similar material to fillmaterial 120. In certain embodiments, in addition to the photo-activatedagent generator, overcoat film 122 may include a polymer resin that hasa solubility in a solvent (to be used subsequently to remove ade-protected portion of fill material 120 in recess 110) that is similarto the solubility of the de-protected fill material 120 in the solvent,so that the de-protected portion of fill material 120 and overcoat film122 can be removed in one step. In certain embodiments, thephoto-activated agent generator of overcoat film 122 is pre-formulatedin the material (e.g., the resin) of overcoat film 122.

As shown in FIG. 1D at stage 104 d, overcoat film 122 is exposed toactinic radiation 124 for a suitable time period. In particular,overcoat film 122 is exposed to sufficient actinic radiation 124 tocause the photo-activated agent generator (e.g., the PAG) in overcoatfilm 122 to generate a solubility-changing agent 126 (e.g., acid) withinovercoat film 122 such that overcoat film 122 now includessolubility-changing agent 126. Solubility-changing agent 126 causesovercoat film 122 to become solubilized, such that overcoat film 122 isnow soluble in one or more solvents to be used in a subsequent removalprocess.

Actinic radiation 124 may include light at a suitable wavelength andhaving other suitable characteristics to activate the photo-activatedagent generator (e.g., the PAG) in overcoat film 122, causing thephoto-activated agent generator in overcoat film 122 to generatesolubility-changing agent 126 (e.g., acid) within overcoat film 122.Characteristics of actinic radiation 124 that may affect whether thephoto-activated agent generator in overcoat film 122 is activated togenerate solubility-changing agent 126 within overcoat film 122 (and inwhat quantities) include content of overcoat film 122, the type ofphoto-activated agent generator, the wavelength of actinic radiation124, the time period for which overcoat film 122 is exposed to actinicradiation 124, and other suitable factors.

A predetermined photo-activated agent generator (e.g., PAG) may besensitive to either a predetermined wavelength or to a predeterminedrange of wavelengths, permitting the use of various exposure sources. Asjust one example, the wavelength of actinic radiation 124 may be in arange of about 170 nm to about 405 nm, and exposure time may be about 10seconds to about a minute (for a wafer of which the portion shown inFIGS. 1A-1J is a part). The polymer of fill material overcoat film 122can be transparent or near-transparent to the predetermined wavelength.

It should be understood, however, that the values and actinic radiationsources are provided as examples only. In certain embodiments, asdescribed below with reference to FIGS. 4B and 4F, substrate 100 is partof a larger substrate, and actinic radiation 124 is part of a largerpattern of actinic radiation that is directed to an overcoat film (ofwhich overcoat film 122 is a part) on the larger substrate. Exposure toactinic radiation (e.g., light) can be executed with a scanner using amask-based exposure, or via a direct-write exposure step, or a floodexposure, as just a few examples. A physical lithographic exposurestepper or scanner can be used as well. In another example, a comparablysimple scanning laser system could be used that can vary the exposureenergy spatially across a surface of a wafer. The particular wavelengthof and exposure time to actinic radiation 124 suitable for a givenimplementation may be affected by the tool used, including the intensityof the laser.

As shown in FIG. 1E at stage 104 e, to modify at least a portion of fillmaterial 120 to be soluble in a solvent to be used in a later removalprocess, solubility-changing agent 126 has diffused into fill material120, causing a portion (de-protected portion 120 a) of fill material 120to become soluble to the solvent to be used in a later removal process.De-protected portion 120 a is generally shown as the portion of fillmaterial 120 into which solubility-changing agent 126 has diffused.Diffusion of solubility-changing agent 126 into fill material 120results in solubility-changing reactions within fill material 120 to thedepth at which solubility-changing agent 126 (e.g., to the predetermineddepth) diffuses into fill material 120, resulting in de-protectedportion 120 a. De-protected portion 120 a of fill material 120 thenbecomes soluble to one or more particular solvents, which also may bereferred to as developers. The de-protection reaction resulting from thediffusion of solubility changing agent 126 into a portion of fillmaterial 120 (creating de-protected portion 120 a) could be ade-crosslinking reaction within the portion of fill material 120. Asimilar reaction may occur within overcoat film 122 to cause overcoatfilm 122 to become solubilized.

Solubility-changing agent 126 may be diffused into fill material 120using any suitable process. In certain embodiments, a thermal process(e.g., heat 127) is used to diffuse solubility-changing agent 126 intoat least a portion of fill material 120. For example, to apply heat 12,substrate 100 may be baked, and the heat associated with bakingsubstrate 100 causes solubility-changing agent 126 to diffuse into atleast a portion of fill material 120. Substrate 100 may be baked via asubstrate plate in a suitable tool, via ambient heat in a substrateprocessing chamber of a suitable tool, a combination of these, or in anyother suitable manner.

In certain embodiments, solubility-changing agent 126 is diffused apredetermined depth into fill material 120 to modify the solubility offill material 120 to the predetermined depth. The predetermined depthmight or might not be sufficient to reach target height 121 for fillmaterial 120 in recess 110. In the illustrated example, thepredetermined depth of stage 104 e is insufficient to recess fillmaterial 120 to target height 121 of fill material 120 in recess 110.

The depth to which solubility-changing agent 126 is diffused into fillmaterial 120 may be affected by and/or controlled using a variety offactors, including the content of overcoat film 122 (including the typeof the photo-activated agent generator in overcoat film 122, otheringredients of overcoat film 122, and concentration of thephoto-activated agent generator in overcoat film 122), characteristicsof actinic radiation 124 (e.g., used at stage 104 d, or later stages),content of fill material 120, width 118 in relation to a differencebetween height 116 and 114 (which may be referred to as the aspect ratioof recess 110 and may affect the ability of actinic radiation 124 toactivate the photo-activated agent generator to generatesolubility-changing agent 126, particularly as fill material 120 hasbeen recessed into recess 110 at later stages), exposure dose of actinicradiation 124, heating (e.g., bake) time and temperature, and any of avariety of other factors.

As shown in FIGURE F at stage 104 f, overcoat film 122 and de-protectedportion 120 a of fill material 120 have been removed. In certainembodiments, overcoat film 122 and de-protected portion 120 a of fillmaterial 120 are developed using a solvent 128, causing overcoat film122 and de-protected portion 120 a of fill material 120 to be removedfrom substrate 100.

This disclosure contemplates solvent 128 including any suitablesubstance for removing overcoat film 122 and de-protected portion 120 aof fill material 120. As just one example, solvent 128 may include anaqueous solution of tetramethyl ammonium hydroxide that is capable ofsolubilizing an acid-deprotected resin (e.g., de-protected portion 120 aof fill material 120). Solvent 128 also may be referred to as adeveloper.

Removal of overcoat film 122 and de-protected portion 120 a of fillmaterial 120 causes a change in height of fill material 120 in recess110 commensurate with exposure dose (e.g., the depth of diffusion ofsolubility-changing agent 126 into fill material 120, or the depth ofde-protected portion 120 a of fill material 120).

This process of depositing overcoat film 122 (stage 104 c), exposure toactinic radiation 124 (stage 104 d), diffusion via baking for a timeperiod (stage 104 e), and development of a de-protected portion of fillmaterial 120 (stage 1040 may be repeated until a cumulative depth offill material 120 de-protection and development (removal) reaches targetheight 121 such that remaining fill material 120 in recess 110 isapproximately at target height 121. For example, FIGS. 1G-1J illustratea second iteration of this cyclic process, which in this example issufficient to achieve target height 121 of fill material 120 in recess110.

In particular, FIG. 1G illustrates stage 104 g in which overcoat film122 has again been deposited on substrate 100. Overcoat film 122 againcontains a photo-activated agent generator (e.g., a PAG) that generates,in response to actinic radiation, a solubility-changing agent (e.g.,acid) for changing the solubility of the material of overcoat film 122and/or fill material 120 to be soluble in one or more solvents to beused in a subsequent removal process.

FIG. 1H illustrates stage 104 h in which overcoat film 122 is exposed toactinic radiation 124, causing the photo-activated agent generator inovercoat film 122 to generate solubility-changing agent 126 withinovercoat film 122 such that overcoat film 122 now includessolubility-changing agent 126 and causing overcoat film 122 to becomesolubilized (soluble in one or more solvents to be used in a subsequentremoval process).

FIG. 1I illustrates stage 104 i in which solubility-changing agent 126has diffused into fill material 120, causing a further portion(de-protected portion 120 b) of fill material 120 to become soluble to asolvent (e.g., solvent 128). De-protected portion 120 b is generallyshown as the portion of fill material 120 into which solubility-changingagent 126 has diffused. As described above, solubility-changing agent126 may be diffused into fill material 120 using a thermal process(e.g., baking of substrate 100). In certain embodiments,solubility-changing agent 126 is diffused a predetermined depth intofill material 120 to modify the solubility of fill material 120 to thepredetermined depth. In this example, the predetermined depth issufficient to de-protect fill material 120 to target height 121.

FIG. 1J illustrates stage 104 j in which overcoat film 122 andde-protected portion 120 b of fill material 120 have been removed. Incertain embodiments, overcoat film 122 and de-protected portion 120 a offill material 120 are developed using solvent 128, causing overcoat film122 and de-protected portion 120 a of fill material 120 to be removedfrom substrate 100. In this example, removal of overcoat film 122 andde-protected portion 120 b of fill material 120 causes a change inheight of fill material 120 in recess 110 such that the remaining fillmaterial 120 in recess 110 is substantially at target height 121.

Although in the illustrated example, two iterations of the cyclicprocess are sufficient to achieve target height 121 of fill material 120in recess 110, this disclosure contemplates any suitable number ofiterations being sufficient to reach target height 121 for a givenapplication. For example, more than two iterations may be appropriate toremove sufficient fill material 120 to reach target height 121 of fillmaterial in recess 110. In another example, a single iteration (e.g., ofstages 104 b-104 f) may be adequate to remove sufficient fill material120 to reach target height 121 of fill material in recess 110.Furthermore, the predetermined depth of diffusion of solubility-changingagent 126 into fill material 120 and subsequent removal of ade-protected portion of fill material 120 may be the same from oneiteration to the next (and potentially across all iterations) or mayvary from one iteration to the next (and potentially across alliterations), according to particular needs.

Subsequent processing may then be performed on semiconductor substrate100. For example, process 102 may be integrated into a process forforming a semiconductor device using a variety of deposition and etchprocesses.

FIGS. 2A-2I illustrate cross-sectional and plan views of substrate 100during an example process 202 for processing substrate 100, according tocertain embodiments. In particular, process 202 includes one or moreiterations of using a PAG-based process (e.g., process 102) forlocational de-protection of portions of fill material 120 and one ormore subsequent iterations of a TAG-based process for de-protection ofportions of fill material 120.

FIGS. 2A-2F generally correspond to FIGS. 1A-1F, and details describedabove with respect to FIGS. 1A-1F that are not repeated are incorporatedby reference. In general, FIGS. 2A-2F illustrate an iteration ofreceiving substrate 100 (stage 204 a); depositing fill material 120 oversubstrate 100 (fill material 120 filling recess 110 and coveringstructures 108, fill material 120 being initially resistant todevelopment by solvent 128) (stage 204 b); depositing overcoat film 122(containing a photo-activated agent generator (e.g., PAG) thatgenerates, in response to actinic radiation 124, solubility-changingagent 126 (e.g., acid)) on substrate 100 (stage 204 c); exposingovercoat film 122 to actinic radiation 124 to generatesolubility-changing agent 126 within overcoat film 122 (stage 204 d);diffusing (e.g., by exposing substrate 100 to heat) solubility-changingagent 126 a predetermined depth into fill material 120, causing aportion (e.g., de-protected portion 120 a) of fill material 120 tobecome soluble to solvent 128) (stage 204 e); and developing overcoatfilm 122 and de-protected portion 120 a of fill material 120 usingsolvent 128, causing overcoat film 122 and de-protected portion 120 a offill material 120 to be removed from substrate 100 (stage 204 f). Thatis, FIGS. 2A-2F illustrate an iteration of a PAG-based process forremoving a portion of fill material 120 in recess 110.

FIGS. 2G-2I illustrate a TAG-based process, which may be performed oneor more times, for removing additional portions of fill material 120 inrecess 110 until target height 121 is reached. As shown in FIG. 2G atstage 204 g, an overcoat film 222 has been deposited on substrate 100.Overcoat film 222 may be deposited in any suitable manner, includingspin-on deposition (or spin-coating), spray-coating, roll-coating, CVD,or any other suitable deposition technique. Overcoat film 222 contains athermally-activated agent generator that generates, in response to heat,a solubility-changing agent for changing the solubility of anothermaterial (e.g., the material of overcoat film 222 and/or fill material120) to be soluble in one or more solvents to be used in a subsequentremoval process. In certain embodiments, the thermally-activated agentgenerator is a TAG and the solubility-changing agent is acid.

Aside from the thermally-activated agent generator, overcoat film 222might or might not include the same material as or similar material tofill material 120. In certain embodiments, in addition to thethermally-activated agent generator, overcoat film 222 may include apolymer resin that has a solubility in a solvent (to be usedsubsequently to remove a de-protected portion of fill material 120) thatis similar to the solubility in the solvent of the de-protected fillmaterial 120, so that the de-protected portion of fill material 120 andovercoat film 222 can be removed in one step. In certain embodiments,the thermally-activated agent generator of overcoat film 222 ispre-formulated in the resin of overcoat film 222.

As shown in FIG. 2H at stage 204 h, overcoat film 222 is exposed to heat127 for a suitable time period. In particular, overcoat film 222 isexposed to sufficient heat 12 to cause the thermally-activated agentgenerator (e.g., the TAG) in overcoat film 222 to generate asolubility-changing agent 226 (e.g., acid) within overcoat film 222 suchthat overcoat film 222 now includes solubility-changing agent 226.Solubility-changing agent 226 causes overcoat film 222 to becomesolubilized, such that overcoat film 222 is now soluble in one or moresolvents to be used in a subsequent removal process. In certainembodiments, a thermal process (e.g., heat 127) is used to activate thethermally-activated agent generator within overcoat film 222. Forexample, to apply heat 12, substrate 100 may be baked, and the heatassociated with baking substrate 100 causes the thermally-activatedagent generator to generate solubility-changing agent 226 withinovercoat film 222. Substrate 100 may be baked via a substrate plate in asuitable tool, via ambient heat in a substrate processing chamber of asuitable tool, a combination of these or in any other suitable manner.

Continuing with stage 204 h in FIG. 2H, in addition to causing thethermally-activated agent generator in overcoat film 222 to generatesolubility-changing agent 226 within overcoat film 222, the thermalprocess applied to (e.g., heating of) substrate 100 also causessolubility-changing agent 226 to diffuse a predetermined depth into fillmaterial 120. Diffusion of solubility-changing agent 226 into fillmaterial 120 modifies at least a portion (de-protected portion 220 a) offill material 120 to be soluble in a solvent to be used in a laterremoval process. De-protected portion 220 a is generally shown as theportion of fill material 120 into which solubility-changing agent 226has diffused. Diffusion of solubility-changing agent 226 into fillmaterial 120 results in solubility-changing reactions within fillmaterial 120 to the depth at which solubility-changing agent 226 (e.g.,to the predetermined depth) diffuses into fill material 120, resultingin de-protected portion 220 a. De-protected portion 220 a of fillmaterial 120 then becomes soluble to one or more particular solvents,which also may be referred to as developers. The de-protection reactionresulting from the diffusion of solubility changing agent 226 into aportion of fill material 120 (creating de-protected portion 220 a) couldbe a de-crosslinking reaction within the portion of fill material 120. Asimilar reaction may occur within overcoat film 222 to cause overcoatfilm 222 to become solubilized.

In certain embodiments, solubility-changing agent 226 is diffused apredetermined depth into fill material 120 to modify the solubility offill material 120 to the predetermined depth. The predetermined depthmight or might not be sufficient to reach target height 121 for fillmaterial 120 in recess 110. In the illustrated example, thepredetermined depth of stage 204 h is sufficient to recess fill material120 to target height 121 of fill material 120 in recess 110. Inembodiments in which the predetermined depth of stage 204 h isinsufficient to recess film material 120 to target height 121 of fillmaterial 120 in recess 110, one or more additional iterations of stages204 g-204 i may be performed.

The depth to which solubility-changing agent 226 is diffused into fillmaterial 120 may be affected by and/or controlled using a variety offactors, including the content of overcoat film 222 (including the typeof the thermally-activated agent generator in overcoat film 222, otheringredients of overcoat film 222, and concentration of thethermally-activated agent generator in overcoat film 222), thetemperature of heat 127, the length of time for which substrate 100 isexposed to heat 127 (e.g., the time period of the bake), content of fillmaterial 120, and any of a variety of other factors.

In certain embodiments, as described below with reference to FIG. 5A-5C,substrate 100 is part of a larger substrate, and heat 127 is appliedacross multiple (and potentially all) portions of the larger substrate.Exposure to heat 12 may cause a substantially uniform amount ofsolubility-changing agent 226 to be generated within overcoat film 222.Furthermore, exposure to heat 127 may cause a substantially uniformdepth of diffusion of solubility-changing agent 226 into fill material120.

As shown in FIG. 2I at stage 204 i, overcoat film 222 and de-protectedportion 220 a of fill material 120 have been removed. In certainembodiments, overcoat film 222 and de-protected portion 220 a of fillmaterial 120 are developed using a solvent 228, causing overcoat film222 and de-protected portion 220 a of fill material 120 to be removedfrom substrate 100.

This disclosure contemplates solvent 228 including any suitablesubstance for removing overcoat film 222 and de-protected portion 220 aof fill material 120. As just one example, solvent 228 may include anaqueous solution of tetramethyl ammonium hydroxide that is capable ofsolubilizing an acid-deprotected resin (e.g., de-protected portion 220 aof fill material 120). In certain embodiments, if a resin (e.g., fillmaterial 120) is designed to interact with a solubility changing agentother than an acid generator, then it may be possible to use an organicsolvent as solvent 228. Solvent 228 might or might not be the same assolvent 128. Solvent 228 also may be referred to as a developer.

Removal of overcoat film 222 and de-protected portion 220 a of fillmaterial 120 causes a change in height of fill material 120 in recess110 commensurate with exposure dose (e.g., the depth of diffusion ofsolubility-changing agent 226 into fill material 120, or the depth ofde-protected portion 220 a of fill material 120). In this example,removal of overcoat film 122 and de-protected portion 120 b causes achange in height of fill material 120 in recess 110 such that theremaining fill material 120 in recess 110 is substantially at targetheight 121.

This process of depositing overcoat film 222 (stage 204 g), heatingsubstrate 100 (stage 204 h), and subsequent development of de-protectedportion 120 a of fill material 120 (stage 204 i) is repeated until acumulative depth of fill material 120 de-protection and developmentreaches target height 121. For example, FIGS. 2G-2I illustrate a firstiteration of this cyclic TAG-based process, which in this example issufficient to achieve target height 121 of fill material 120 in recess110. In other examples, additional iterations TAG-based may be used toremove sufficient fill material 120 to reach target height 121 of fillmaterial in recess 110.

Although in the illustrated example of FIGS. 2A-2I a single iteration ofusing the photo-activated solubility-changing agent-generatingingredient (the PAG-based process) is illustrated and described, thisdisclosure contemplates process 202 including multiple iterations ofusing the photo-activated solubility-changing agent-generatingingredient prior to one or more iterations using the thermally-activatedagent generator (the TAG-based process) to achieve target height 121 offill material 120 in recess 110, according to particular needs.Furthermore, whether considering the PAG-based process or the TAG-basedprocess, the predetermined depth of diffusion of solubility-changingagent 126/226 into fill material 120 and subsequent removal of ade-protected portion of fill material 120 may be the same from oneiteration to the next (and potentially across all iterations) or mayvary from one iteration to the next (and potentially across alliterations), according to particular needs.

Subsequent processing may then be performed on semiconductor substrate100. For example, process 202 may be integrated into a process forforming a semiconductor device using a variety of deposition and etchprocesses.

FIG. 3 illustrates example effects of varying depths of diffusion of asolubility-changing agent 126/226 into fill material 120, according tocertain embodiments. In general, FIG. 3 illustrates that, according tocertain embodiments, as the depth of diffusions of solubility-changingagent 126/226 (e.g., acid) into fill material 120 increases, anincreasing amount of fill material 120 is removed during a subsequentdevelopment process, which decreases the height of post-development fillmaterial 120 in recess 110. Portions of fill material 120 into whichsolubility-changing agent 126/226 (e.g., acid) diffused become solubleto solvent 128/228, which allows solvent 128/228 to remove thoseportions of fill material 120 when fill material 120 is developed usingsolvent 128/228. The example embodiments control film height by locationthrough acid diffusion into an acid solubility-changeable resin layer inwhich a greater degree of acid diffusion results in a larger change infilm thickness per overcoat cycle. Thus, by controlling the depth ofdiffusion of solubility-changing agent 126/226 into fill material 120,the amount of fill material 120 removed (e.g., de-protected portion 120a/120 b/220 a) in a subsequent removal process can be controlled.Factors potentially affecting the depth of diffusions are describedabove.

FIGS. 4A-4H illustrate cross-sectional views of example substrateportions 400 a-400 d having pre-patterned features during exampleprocess 102 (described above with reference to FIGS. 1A-1J) forprocessing substrate portions 400 a-400 d, according to certainembodiments. For ease of reference, substrate portions 400 a-400 d maybe referred to collectively as substrate 400. Substrate portions 400a-400 d may be part of a same substrate 400, or may be part of differentsubstrates 400. Substrate 400 may be part of a larger semiconductordevice, such as part of a larger semiconductor wafer. Furthermore,substrate portions 400 a-400 d may be part of a same semiconductor waferor one or more different semiconductor wafers. In certain embodiments,process 102 includes repeatedly performing a PAG-based process to removea fill material from a recess 110 of substrate 400 until the fillmaterial is a predetermined height within the recess 110. To the extentnot repeated, details related to substrate 100 and process 102 describedwith reference to FIGS. 1A-1J (or elsewhere) are incorporated byreference.

As shown in FIG. 4A, in addition to base portion 106, substrate 400includes multiple structures 108 that define multiple recesses 110.Although structures 108 are shown as generally having the same shapes,heights, and pitches, structures 108 may have any suitable shapes,heights, and/or pitches, including varying shapes, heights, and/orpitches. Additionally, although recesses 110 are shown as generallyhaving the same shapes and depths, recesses 110 may have any suitableshapes and/or depths, including varying shapes and/or depths. Thisdisclosure contemplates the structures 108 being patterned into anysuitable features.

As shown in FIG. 4A (corresponding to stage 104 c), fill material 120has been deposited on substrate 400, with fill material 120 fillingrecesses 110 and covering structures 108, and overcoat film 122 has beendeposited on substrate 400. In subsequent photolithography steps, it maybe desirable to recess, via photolithographic development techniques,fill material 120 into recesses 110, such that fill material 120 has aparticular height within recesses 110. A target height 121 for recessingfill material 120 within recesses 110 is indicated for each recess 110.In this example, a different target height 121 is desired for eachrecess 110, with little or no recessing of fill material 120 beingdesired for the right-most recess 110 in FIG. 4A. This disclosurecontemplates a same target height 121 being desired for two or more (andpotentially all) recesses 110, however.

As described above, overcoat film 122 contains a photo-activated agentgenerator (e.g., a PAG) that generates, in response to actinic radiation124, a solubility-changing agent 126 (e.g., acid) for changing thesolubility of overcoat film 122 and/or fill material 120 to be solublein one or more solvents (e.g., solvent 128) to be used in a subsequentremoval process.

As shown in FIG. 4B (corresponding to stage 104 d), overcoat film 122 isexposed to sufficient actinic radiation 124 for a sufficient time periodto cause, where desired, the photo-activated agent generator (e.g., thePAG) in overcoat film 122 to generate solubility-changing agent 126(e.g., acid) within overcoat film 122 such that overcoat film 122 nowincludes solubility-changing agent 126. In the example of FIG. 4B,actinic radiation 124 is a pattern of actinic radiation that is directedto overcoat film 122.

As described above, characteristics of actinic radiation 124 affect theamount of the photo-activated agent generator in overcoat film 122 thatis activated. That is actinic radiation 124 having certaincharacteristics causes greater amounts of the photo-activated agentgenerator in overcoat film 122 to be activated, resulting in greateramounts of solubility-changing agent 126 being generated in those areasof overcoat film 122. Actinic radiation 124 having certain othercharacteristics causes lesser amounts of the photo-activated agentgenerator in overcoat film 122 to be activated, resulting in lesssolubility-changing agent 126 being generated in those areas of overcoatfilm 122. The amount of solubility-changing agent 126 in a particulararea of overcoat film 122 affects how much solubility-changing agent 126will be available for diffusion into fill material 120 in a subsequentheating step.

Thus, a pattern of actinic radiation 124 can be tailored to activategreater amounts of the photo-activated agent generator in overcoat film122 overlying areas of fill material 120 where greater depth ofdiffusion of solubility-changing agent 126 and ultimately removal offill material is desired and to activate lesser amounts of thephoto-activated agent generator in overcoat film 122 overlying areas offill material 120 where lesser depth of diffusion of solubility-changingagent 126 and ultimately removal of fill material is desired. Althoughuse of a pattern of actinic radiation 124 to vary the depth of diffusionof solubility-changing agent 126 and ultimately remove of fill material120 is described, the pattern of actinic radiation 124 could be designedto cause the photo-activated agent generator in overcoat film 122 togenerate solubility-changing agent 126 in substantially equal amounts inone or more portions of overcoat film 122, such as when the targetheight 121 for fill material 120 in recesses 110 underlying those one ormore portions of overcoat film 122 is substantially the equal.

In the example illustrated in FIG. 4B, the pattern of actinic radiation124 is designed to cause the photo-activated agent generator in overcoatfilm 122 to generate a decreasing amount of solubility-changing agent126 from overcoat film 122 over substrate portion 400 a (the left sideof FIG. 4A) to overcoat film 122 over substrate portion 400 d (the rightside of FIG. 4A), with little to no solubility-changing agent 126 beinggenerated over recess 110 of substrate portion 400 d (as no actinicradiation 124 is applied over substrate portion 400 d). In certainembodiments, the ability to control activation of the photo-activatedagent generator in overcoat film 122 and subsequent diffusion (e.g., byadjusting the exposure dose of actinic radiation 124) may be affected bya resolution limit of an exposure tool.

As shown in FIG. 4C (corresponding to stage 104 e), to modify at least aportion of fill material 120 to be soluble in solvent 128,solubility-changing agent 126 has diffused into fill material 120,causing a portion (de-protected portion 420 a) of fill material 120 tobecome soluble to solvent 128. De-protected portion 420 a is generallyshown as the portions of fill material 120 into whichsolubility-changing agent 126 has diffused. In certain embodiments,solubility-changing agent 126 is caused to diffuse into at least aportion of fill material 120 (creating de-protected portion 420 a) usinga thermal process (e.g., application of heat 12 for a suitable timeperiod). In the example shown in FIG. 4C, solubility-changing agent 126is diffused into recesses 110 at varying predetermined depths.Additionally, the predetermined depths in this example are insufficientto recess fill material 120 to target heights 121 of fill material 120in recesses 110.

As illustrated in FIG. 4D (corresponding to stage 104 f), overcoat film122 and de-protected portion 420 a of fill material 120 have beenremoved. In certain embodiments, overcoat film 122 and de-protectedportion 420 a of fill material 120 are developed using solvent 128,causing overcoat film 122 and de-protected portion 420 a of fillmaterial 120 to be removed from substrate 400. Removal of overcoat film122 and de-protected portion 420 a of fill material 120 causes changesin height of fill material 120 in recesses 110 commensurate withexposure dose (e.g., the depth of diffusion of solubility-changing agent126 into fill material 120, or the depth of de-protected portions 420 aof fill material 120).

This process of depositing overcoat film 122, exposure to actinicradiation 124, diffusion via baking for a length of time, and subsequentdevelopment of de-protected portion 120 a of fill material 120 isrepeated until a cumulative depth of fill material 120 de-protection anddevelopment in each recess 110 reaches corresponding target heights 121.For example, FIGS. 4E-4H illustrate a second iteration of this cyclicprocess, which in this example is sufficient to achieve target heights121 of fill material 120 in recesses 110. Additional or fewer iterationsmay be appropriate to remove sufficient fill material 120 to reachtarget heights 121 of fill material in recesses 110 in particularimplementations. Furthermore, the predetermined depth of diffusion ofsolubility-changing agent 126 into fill material 120 and subsequentremoval of a de-protected portion of fill material 120 may be the samefrom one iteration to the next (and potentially across all iterations)or may vary from one iteration to the next (and potentially across alliterations), according to particular needs.

In particular, as illustrated in FIG. 4E (corresponding to stage 104 g),overcoat film 122 has again been deposited on substrate 400. Overcoatfilm 122 again contains a photo-activated agent generator (e.g., a PAG)that generates, in response to actinic radiation 124, asolubility-changing agent 126 (e.g., acid) for changing the solubilityof the material of overcoat film 122 and/or fill material 120 to besoluble in solvents 128.

As illustrated in FIG. 4F (corresponding to stage 104 h), overcoat film122 is exposed to a pattern of actinic radiation 124, causing thephoto-activated agent generator in overcoat film 122 to generatesolubility-changing agent 126 within overcoat film 122 such thatovercoat film 122 now includes solubility-changing agent 126 and causingovercoat film 122 to become solubilized (soluble in solvent 128). Itshould be understood that the pattern of actinic radiation 124 used inFIG. 4F might or might not be the same as the pattern of actinicradiation 124 used in FIG. 4B, depending on the desired predetermineddepth of diffusion of solubility-changing agent 126 into fill material120 in a subsequent processing step.

As illustrated in FIG. 4G (corresponding to stage 104 i),solubility-changing agent 126 has diffused into fill material 120,causing a further portion (de-protected portion 420 b) of fill material120 to become soluble to solvent 128. De-protected portion 420 b isgenerally shown as the portion of fill material 120 into whichsolubility-changing agent 126 has diffused. As described above,solubility-changing agent 126 may be diffused into fill material 120using a thermal process (e.g., baking of substrate 400). In certainembodiments, solubility-changing agent 126 is diffused a predetermineddepth into fill material 120 to modify the solubility of fill material120 to the predetermined depth, and in this example, the predetermineddepth is sufficient to de-protect fill material 120 to target heights121 in recesses 110.

As illustrated in FIG. 4H (corresponding to stage 104 j), overcoat film122 and de-protected portion 420 b of fill material 120 have beenremoved. In certain embodiments, overcoat film 122 and de-protectedportion 420 a of fill material 120 are developed using solvent 128,causing overcoat film 122 and de-protected portion 420 a of fillmaterial 120 to be removed from substrate 400. In this example, removalof overcoat film 122 and de-protected portion 120 b of fill material 120causes changes in height of fill material 120 in recesses 110 such thatthe remaining fill material 120 in recesses 110 is substantially attarget heights 121.

Subsequent processing may then be performed on semiconductor substrate400. For example, process 102 may be integrated into a process forforming a semiconductor device using a variety of deposition and etchprocesses.

Process 102 may provide one or more technical advantages. For example,removing fill material 120 by creating de-protected portions of fillmaterial 120 using a solubility-changing agent 126 that is generatedfrom a photo-activated agent in an overcoat film 122 may provide aprecise way to change the height of fill material 120. As anotherexample, the ability to direct a pattern of actinic radiation 124 towardovercoat film 122 may allow fill material 120 to be removed at differingprecise depths within one or more of recesses 110, and ultimately allowdifferent target heights 121 to be reached.

FIGS. 5A-5C illustrate cross-sectional views of example substrateportions 400 a-400 d having pre-patterned features during portions ofexample process 202 (described above with reference to FIGS. 2A-1I) forprocessing substrate portions 400 a-400 d, according to certainembodiments. In certain embodiments, process 202 includes one or moreiterations of performing a PAG-based process to establish potentiallyvarying heights (by removing fill material 120 to varying depths inrecesses 110) of fill material 120 on various substrate portions 400a-400 d and one or more subsequent iterations of performing a TAG-basedprocess to potentially uniformly remove portions of fill material 120 onvarious substrate portions 400 a-400 d. To the extent not repeated,details related to substrate 100, process 202, and substrate portions400 a-400 d/substrate 400 described with reference to FIGS. 2A-2I and/orFIGS. 4A-4H (or elsewhere) are incorporated by reference.

Rather than beginning at stage 202 a of process 202, FIG. 5A begins at astep analogous to stage 204 g of FIG. 2G. That is, FIG. 5A illustratessubstrate 400 following at least one iteration of a PAG-based process toremove a portion of fill material 120 to varying predetermined depthswithin recesses 110, setting different relative heights of remainingfill material 120 in recesses 110. For example, just prior to the stateof substrate 400 illustrated in FIG. 5A, substrate 400 may be in a statecorresponding to FIG. 4D. FIGS. 5A-5C illustrate a TAG-based process,which may be performed one or more times, for removing additionalportions of fill material 120 in recess 110 until target height 121 isreached.

As shown in FIG. 5A (corresponding to stage 204 g), an overcoat film 222has been deposited on substrate 400. Overcoat film 222 contains athermally-activated agent generator (e.g., a TAG) that generates, inresponse to heat, solubility-changing agent 226 (e.g., acid) forchanging the solubility of another material (e.g., the material ofovercoat film 222 and/or fill material 120) to be soluble in solvent 228to be used in a subsequent removal process.

As shown in FIG. 5B (corresponding to stage 204 h), overcoat film 222 isexposed to sufficient heat 127 for a suitable time period to cause thethermally-activated agent generator (e.g., the TAG) in overcoat film 222to generate solubility-changing agent 226 (e.g., acid) within overcoatfilm 222 such that overcoat film 222 now includes solubility-changingagent 226. The thermal process applied to (e.g., heating of) substrate400 also causes solubility-changing agent 226 to diffuse a predetermineddepth into fill material 120. Diffusion of solubility-changing agent 226into fill material 120 modifies at least a portion (de-protected portion520 a) of fill material 120 to be soluble in solvent 228. De-protectedportion 520 a is generally shown as the portion of fill material 120into which solubility-changing agent 226 has diffused.

In certain embodiments, solubility-changing agent 226 is diffused apredetermined depth into fill material 120 to modify the solubility offill material 120 to the predetermined depth. The predetermined depthmight or might not be sufficient to reach target heights 121 for fillmaterial 120 in recesses 110. In the illustrated example, thepredetermined depth is sufficient to recess fill material 120 to targetheights 121 of fill material 120 in recesses 110. In embodiments inwhich the predetermined depth is insufficient to recess film material120 to target heights 121 in recesses 110, one or more additionaliterations of the process illustrated in FIGS. 5A-5C may be performed.

In certain embodiments, heat 127 is applied across substrate 400, andexposure to heat 12 may cause a substantially uniform amount ofsolubility-changing agent 226 to be generated within overcoat film 222.Furthermore, exposure to heat 127 may cause a substantially uniformdepth of diffusion of solubility-changing agent 226 into fill material120.

As shown in FIG. 5C (corresponding to stage 204 i), overcoat film 222and de-protected portion 420 a of fill material 120 have been removed.In certain embodiments, overcoat film 222 and de-protected portion 420 aof fill material 120 are developed using solvent 228, causing overcoatfilm 222 and de-protected portion 420 a of fill material 120 to beremoved from substrate 400. In this example, removal of overcoat film122 and de-protected portion 120 b of fill material 120 causes a changein height of fill material 120 in recess 110 such that the remainingfill material 120 in recesses 110 is substantially at target heights121.

This process of depositing overcoat film 222, heating of substrate 400,and subsequent development of de-protected portion 520 a of fillmaterial 120 is repeated until a cumulative depth of fill material 120de-protection and development in recesses 110 reaches correspondingtarget heights 121. For example, FIGS. 5A-5C illustrate a firstiteration of this cyclic process, which in this example is sufficient toachieve target heights 121 of fill material 120 in recesses 110.Additional or fewer iterations may be appropriate to remove sufficientfill material 120 to reach target heights 121 of fill material inrecesses 110 in particular implementations. Furthermore, thepredetermined depth of diffusion of solubility-changing agent 226 intofill material 120 and subsequent removal of a de-protected portion offill material 120 may be the same from one iteration to the next(potentially across all iterations) or may vary from one iteration tothe next (potentially across all iterations), according to particularneeds.

Subsequent processing may then be performed on semiconductor substrate400. For example, process 202 may be integrated into a process forforming a semiconductor device using a variety of deposition and etchprocesses.

Process 202 may provide one or more technical advantages, which may bein addition to advantages described above with reference to process 102.In certain embodiments, recess 110 has a high aspect ratio (e.g., thedifference between height 116 and height 114 is significantly largerthan width 118), which can impede a path for the wavelength of light(the actinic radiation 124) suitable for activating the photo-activatedagent generator in overcoat film 122 to reach the photo-activated acidgenerator in overcoat film 122 for activation. In general, a PAG-basedprocess may begin encountering difficulties in activating the PAG inovercoat film 122 when the lateral dimension of the feature (e.g.,recess 110) is much less than the wavelength of the impinging radiation.The greater the aspect ratio of the feature (e.g., recess 110) andthereby the depth in which the photons of actinic radiation 124 are tointeract with overcoat film 122, the lower the efficiency of photoninteraction within the feature at a given dimension less than theincoming wavelength of actinic radiation 124. As just one example, width118 of the gap between structures 108 could be about 20 nm and a depthof recess 110 could be about five times that or more. Athermally-activated agent generator in overcoat film 222, which isactivated by heat 127 rather than actinic radiation 124, does not relyon a particular wavelength of light and generates a substantiallyuniform amount of solubility-changing agent 226 in response tosufficient heat.

In process 202, one or more iterations of a PAG-based process may beperformed to establish relative differences in target heights 121 inrecesses 110 based on locations of recesses 110, while one or moresubsequent iterations of the TAG-based process may be performed tosubstantially uniformly continue recessing fill material 120 in recesses110 until target heights 121 are reached, while maintaining the relativedifferences in target heights 121 established using the one or moreiterations of the PAG-based process. Furthermore, the TAG-based processis particularly efficient, as the thermal process used to activate thethermally-activated agent generator to generate solubility-changingagent 226 also causes solubility-changing agent 226 to diffuse thepredetermined depth into fill material 120 without using a separate step(and potentially a separate tool) for exposure to actinic radiation 124.

FIG. 6 illustrates an example method for processing a semiconductorsubstrate, according to certain embodiments. In general, the methoddescribed with reference to FIG. 6 corresponds to process 102 describedabove with reference to FIGS. 1A-1J and 4A-H.

At step 600, a substrate 100/400 having microfabricated structures 108defining recesses 110 is received. At step 602, fill material 120 isdeposited on substrate 100/400, filling recesses 110 and coveringmicrofabricated structures 108. Fill material 120 may be a resin, and isinitially resistant to development by a solvent 128. At step 604,overcoat film 122 is deposited on substrate 100/400. Overcoat film 122contains a photo-activated agent generator (e.g., a PAG) that generates,in response to actinic radiation, a solubility-changing agent 126 (e.g.,acid).

At step 606, overcoat film 122 is exposed to sufficient actinicradiation 124 to cause the photo-activated agent generator in overcoatfilm 122 to generate solubility-changing agent 126 within overcoat film122. Actinic radiation 124 may be a pattern of actinic radiation 124directed at substrate 100/400 and designed to achieve variation inpredetermined depths of removal (and ultimately remaining heights of)fill material 120 in recesses 110. At step 608, solubility-changingagent 126 is diffused a predetermined depth into fill material 120,causing de-protected portion 120 a/420 a of fill material 120 to becomesoluble to solvent 128. This may include multiple differentpredetermined depths across substrate 100/400. In certain embodiments,substrate 100/400 is baked (or otherwise heated) to causesolubility-changing agent 126 to diffuse the predetermined depth intofill material 120. At step 610, overcoat film 122 and de-protectedportion 120 a/420 a of fill material 120 is developed using solvent 128.

At step 612, a determination is made regarding whether a predeterminedcondition is met. In general, the determination made at step 612 relatesto whether target heights 121 of fill material 120 in recesses 110 havebeen achieved. For example, the predetermined condition may includedetermining whether a predetermined number of cycles of steps 604-610have been performed, the predetermined number of cycles having beenpredetermined to be sufficient to achieve target heights 121 of fillmaterial 120 in recesses 110. As another example, the predeterminedcondition may include a real-time analysis of substrate 100/400 todetermine whether target heights 121 of fill material 120 in recesses110 have been achieved.

If a determination is made at step 612 that the predetermined conditionis not met, then the method returns to step 604 to perform another cycleof steps 604-610. If a determination is made at step 612 that thepredetermined condition has been met, then the method proceeds to step614, with target heights 121 of fill material 120 in recesses 110 havingbeen achieved. At step 614, subsequent semiconductor fabricationprocesses may be performed.

FIG. 7 illustrates an example method for processing a semiconductorsubstrate, according to certain embodiments. In general, the methoddescribed with reference to FIG. 7 corresponds to process 202 describedabove with reference to FIGS. 2A-2I and 5A-5C.

Steps 700-710 generally correspond to steps 600-610 of the methoddescribed with respect to FIG. 6 ; thus, the details of steps 600-610are incorporated by reference and not repeated. At step 712, adetermination is made regarding whether a predetermined condition ismet. For example, the predetermined condition may include determiningwhether a predetermined number of cycles of steps 704-710 have beenperformed. In certain embodiments, the predetermined condition iswhether a single cycle of steps 704-710 (e.g., the PAG-based process)has been performed; however, this disclosure contemplates multiplecycles of steps 704-710 (e.g., the PAG-based process) being performedprior to advancing to step 714.

If a determination is made at step 712 that the predetermined conditionis not met, then the method returns to step 704 to perform another cycleof steps 704-710 (e.g., the PAG-based process). If a determination ismade at step 712 that the predetermined condition has been met, then themethod proceeds to step 714. At step 714, overcoat film 222 is depositedon substrate 100/400. Overcoat film 222 contains a thermally-activatedagent generator (e.g., a TAG) that generates, in response to heat, asolubility-changing agent 226 (e.g., acid). At step 716, substrate100/400 is baked sufficiently to generate solubility-changing agent 226within overcoat film 222, and to diffuse solubility-changing agent 226 apredetermined depth into fill material 120, causing a portion (e.g.,de-protected portion 220 a/520 a) of fill material 120 to become solubleto solvent 228. At step 718, overcoat film 122 and de-protected portion220 a/520 a of fill material 120 is developed using solvent 228.

At step 720, a determination is made regarding whether a predeterminedcondition is met. In general, the determination made at step 720 relatesto whether target heights 121 of fill material 120 in recesses 110 havebeen achieved, and may be analogous to the predetermined conditiondescribed above at step 612 of FIG. 6 . If a determination is made atstep 720 that the predetermined condition is not met, then the methodreturns to step 714 to perform another cycle of steps 714-718. If adetermination is made at step 720 that the predetermined condition hasbeen met, then the method proceeds to step 722, with target heights 121of fill material 120 in recesses 110 having been achieved. At step 722,subsequent semiconductor fabrication processes may be performed.

FIG. 8 illustrates an example method for processing a semiconductorsubstrate, according to certain embodiments. At step 800, fill material120 is deposited on substrate 100/400, filling recesses 110 and coveringmicrofabricated structures 108 of substrate 100/400. At step 802, usinga PAG-based process, a localized removal of fill material 120 isperformed to remove fill material 120 to respective first depths inrecesses 110. At step 804, a determination is made regarding whether apredetermined condition is met. For example, the predetermined conditionmay include determining whether a predetermined number of cycles of step802 have been performed. In certain embodiments, the predeterminedcondition is whether a single cycle of step 802 has been performed;however, this disclosure contemplates multiple cycles of step 802 beingperformed prior to advancing to step 806. If a determination is made atstep 804 that the predetermined condition is not met, then the methodreturns to step 802 to perform another cycle of step 802. If adetermination is made at step 804 that the predetermined condition hasbeen met, then the method proceeds to step 806.

At step 806, using a TAG-based process, a uniform etch of a remainingportion of fill material 120 is performed to remove a substantiallyuniform depth of fill material 120 in recesses 110. At step 808, adetermination is made regarding whether a predetermined condition ismet. In general, the determination made at step 808 relates to whethertarget heights 121 of fill material 120 in recesses 110 have beenachieved, and may be analogous to the predetermined condition describedabove at step 612 and 720 of FIGS. 6 and 7 , respectively. If adetermination is made at step 808 that the predetermined condition isnot met, then the method returns to step 806 to perform another cycle ofstep 806. If a determination is made at step 808 that the predeterminedcondition has been met, then the method proceeds to step 810, withtarget heights 121 of fill material 120 in recesses 110 having beenachieved. At step 810, subsequent semiconductor fabrication processesmay be performed.

FIGS. 9A-9C illustrate example PAGs and TAGs that may be used inovercoat films 122/222, according to certain embodiments. FIG. 9Aillustrates example ionic PAGs, including triphenylsulfonium triflateand Bis(4-tert-butylphenyl)iodonium triflate, that may be used as thephoto-activated agent generator of overcoat film 122. FIG. 9A alsoillustrates example non-ionic PAGs, including N-Hydroxynaphthalimidetriflate and N-Hydroxy-5-norbornene-2,3-dicarboximideperfluoro-1-butanesulfonate, that may be used as the photo-activatedagent generator of overcoat film 122. In general, whether ionic ornon-ionic, PAGs may decompose upon exposure to a specific wavelength (orrange of wavelengths) of light, generating a strong acid. FIG. 9Billustrates example polymer-bound PAGs that may be used as thephoto-activated agent generator of overcoat film 122. FIG. 9Cillustrates example TAGs that may be used as the thermally-activatedagent generator of overcoat film 222. These TAGs may decompose atelevated temperatures, generating a strong acid. In certain embodiments,TAGs may include sulfonate esters, onium salts or halogen-containingcompounds to name just a few examples.

FIGS. 10A-10B illustrate example modification of the solubility ofovercoat films 122/222 and/or fill material 120. In particular, FIGS.10A-10B illustrate polymer-solubility changing interactions with strongacid. FIG. 10A illustrates a tert-butoxycarbonyl (t-BOC) de-protectionchemistry, which may be used in certain photoresists. The material t-BOCmay be one of several monomers that make up the polymer of fill material120 and/or overcoat films 122/222. In this example, the protectedpolymer is hydrophobic (t-butyl group), and the de-protected polymer ishydroxide, carboxylic acid. FIG. 10B illustrates a vinyl etherde-crosslinking, which may be used in certain developable bottomanti-reflective coatings (dBARCs). In certain embodiments, interactionwith strong acid causes a de-crosslinking reaction to occur, making thereacted portion of the film (e.g., fill material 120 and/or overcoatfilms 122/222) more soluble in a given developer (e.g., solvent128/228).

It should be understood that the example chemistries and systemsdescribed above with reference to FIGS. 9A-9C and 10A-10B are providedas examples only, and that this disclosure contemplates using anysuitable chemistries and systems.

Although this disclosure has been described in the context of aparticular microfabrication process (recessing a fill material 120 totarget heights 121 within one or more recesses 110 in a substrate100/400), this disclosure may be used with any suitable microfabricationprocess. For example, this disclosure contemplates using techniquesdescribed herein to control the height of any film or otherstructure/feature of a semiconductor device, whether or not such film orother structure/feature is wholly or partially in a recess.

A specific example application of embodiments herein is the constructionof three-dimensional transistor architectures in which n-type fieldeffect transistors (NFETs) and p-type FETs (PFETs) are stacked on top ofone another. This can include a vertical stack of lateralgate-all-around (GAA) transistors. Epitaxial silicon-germanium (SiGe)growth doped with electron-rich (n-type) species can occur at both upperand lower layers of uncovered silicon. The upper silicon layer, however,can be designed to have electron-deficient (p-type) SiGe. Therefore,after the n-type SiGe is grown, a corresponding feature is filled to adepth that will cover the lower silicon level while leaving the uppersilicon level exposed (uncovered) for subsequent silicon etch andregrowth of p-type SiGe. Use of film height control embodiments hereinmay provide improved control and/or across-wafer uniformity of filmheight. FIG. 11 illustrates examples of stacked transistor architecturesthat may benefit from precise film height control to selectively growboth n-type and p-type SiGe.

The process of SAB is a method to pattern dense features at advancedprocessing nodes. A step in the SAB process flow may benefit from apartial recess of a specific film, such as a spin-on carbon film asillustrated in FIGS. 12A-12B. If this film is over or under etchedrelative to the surrounding spacers by even a small margin, the finalpattern in the process flow might not be transferred correctly,resulting in a failure. Techniques herein provide a highly planarsurface across potentially the entirety of a wafer, which may improvethe control and reproducibility of the SAB process.

Various techniques have been described as multiple discrete operationsto assist in understanding the various embodiments. The order ofdescription should not be construed as to imply that these operationsare necessarily order dependent. Operations described may be performedin a different order than the described embodiment. Various additionaloperations may be performed and/or described operations may be omittedin additional embodiments.

While this disclosure has been described with reference to illustrativeembodiments, this description is not intended to be construed in alimiting sense. Various modifications and combinations of theillustrative embodiments, as well as other embodiments of thedisclosure, will be apparent to persons skilled in the art uponreference to the description. It is therefore intended that the appendedclaims encompass any such modifications or embodiments.

What is claimed is:
 1. A method for processing a semiconductorsubstrate, the method comprising: receiving a substrate havingmicrofabricated structures defining recesses; depositing a resin film onthe substrate, the resin film filling the recesses and covering themicrofabricated structures, the resin film being initially resistant todevelopment by a first solvent; depositing a first overcoat film on thesubstrate, the first overcoat film containing a first agent-generatingingredient that generates, in response to actinic radiation, a firstsolubility-changing agent; exposing the first overcoat film to firstsufficient actinic radiation to generate the first solubility-changingagent within the first overcoat film; diffusing the firstsolubility-changing agent a first predetermined depth into the resinfilm causing a first portion of the resin film to become soluble to thefirst solvent; developing the first overcoat film and the first portionof the resin film using the first solvent; depositing a second overcoatfilm on the substrate, the second overcoat film containing the firstagent-generating ingredient that generates, in response to actinicradiation, the first solubility-changing agent; exposing the secondovercoat film to second sufficient actinic radiation to generate thefirst solubility-changing agent within the second overcoat film;diffusing the first solubility-changing agent a second predetermineddepth into the resin film causing a second portion of the resin film tobecome soluble to the first solvent; and developing the second overcoatfilm and the second portion of the resin film using the first solventresulting in the resin film being recessed respective first combineddepths in the recesses.
 2. The method of claim 1, wherein diffusing thefirst solubility-changing agent the first predetermined depth into theresin film comprises heating the substrate.
 3. The method of claim 1,wherein: diffusing the first solubility-changing agent a secondpredetermined depth into the resin film causing a second portion of theresin film to become soluble to the first solvent comprises: diffusingthe first solubility-changing agent a first depth into a first recess ofthe recesses; and diffusing the first solubility-changing agent a seconddepth into a second recess of the recesses, the first depth beinggreater than the second depth; and developing the second portion of theresin film using the first solvent results in the resin film beingrecessed a greater first combined depth in the first recess than thefirst combined depth in the second recess.
 4. The method of claim 1,wherein the first agent-generating ingredient comprises a photoacidgenerator.
 5. The method of claim 1, wherein the first sufficientactinic radiation and the second sufficient actinic radiation havesubstantially similar characteristics.
 6. The method of claim 1, furthercomprising: depositing a third overcoat film on the substrate, the thirdovercoat film containing a second agent-generating ingredient thatgenerates, in response to heating of the substrate, a secondsolubility-changing agent; heating the substrate sufficiently togenerate the second solubility-changing agent within the second overcoatfilm and diffuse the second solubility-changing agent a thirdpredetermined depth into the resin film causing a third portion of theresin film to become soluble to the first solvent; and developing thethird portion of the resin film using the first solvent resulting in theresin film being recessed respective second combined depths in therecesses.
 7. The method of claim 1, wherein: developing the firstovercoat film and the first portion of the resin film using the firstsolvent removes the first overcoat film and the first portion of theresin film; and developing the second overcoat film and the secondportion of the resin film using the first solvent removes the secondovercoat film and the second portion of the resin film.
 8. A method forprocessing a semiconductor substrate, the method comprising: receiving asubstrate having microfabricated structures defining recesses;depositing a resin film on the substrate, the resin film filling therecesses and covering the microfabricated structures, the resin filmbeing initially resistant to development by a first solvent; depositinga first overcoat film on the substrate, the first overcoat filmcontaining a first agent-generating ingredient that generates, inresponse to actinic radiation, a first solubility-changing agent;exposing the first overcoat film to sufficient actinic radiation togenerate the first solubility-changing agent within the first overcoatfilm; diffusing the first solubility-changing agent a firstpredetermined depth into the resin film causing a first portion of theresin film to become soluble to the first solvent; developing the firstportion of the resin film using the first solvent; depositing a secondovercoat film on the substrate, the second overcoat film containing asecond agent-generating ingredient that generates, in response toheating of the substrate, a second solubility-changing agent; baking thesubstrate sufficiently to generate the second solubility-changing agentwithin the second overcoat film and diffuse the secondsolubility-changing agent a second predetermined depth into the resinfilm causing a second portion of the resin film to become soluble to thefirst solvent; and developing the second portion of the resin film usingthe first solvent resulting in the resin film being recessed respectivecombined depths in the recesses.
 9. The method of claim 8, furthercomprising cyclically removing additional portions of the resin filmuntil the resin film is a respective predetermined thickness in therecesses.
 10. The method of claim 8, wherein: a width of at least one ofthe recesses is about 20 nm or less; and a depth of the at least one ofthe recesses prior to deposition of the resin film on the substrate isat least five times the width of the at least one of the recesses. 11.The method of claim 8, wherein: the first agent-generating ingredientcomprises a photoacid generator; and the second agent-generatingingredient comprises a thermal acid generator.
 12. The method of claim8, wherein: developing the first overcoat film and the first portion ofthe resin film using the first solvent removes the first overcoat filmand the first portion of the resin film; and developing the secondovercoat film and the second portion of the resin film using the firstsolvent removes the second overcoat film and the second portion of theresin film.
 13. A method for processing a semiconductor substrate, themethod comprising: depositing a resin film on a substrate, the substratehaving microfabricated structures defining recesses, the resin filmfilling the recesses and covering the microfabricated structures;performing, using a photoacid generator (PAG)-based process, a localizedremoval of the resin film to remove the resin film to respective firstdepths in the recesses, at least two depths of the respective firstdepths being different depths; and repeatedly performing, using athermal acid generator (TAG)-based process and until a predeterminedcondition is met, a uniform removal of a remaining portion of the resinfilm to remove a substantially uniform depth of the resin film in therecesses.
 14. The method of claim 13, wherein the PAG-based processcomprises: depositing a first overcoat film on the substrate, the firstovercoat film comprising a PAG; exposing the first overcoat film to afirst pattern of radiation to cause the PAG to generate a first acidwithin the first overcoat film according to the first pattern ofradiation; heating the substrate sufficiently to diffuse the first acidinto the resin film to the respective first depths in the recesses,causing a first portion of the resin film to become soluble to a firstsolvent, the first portion extending to the respective first depths inthe recesses; and developing the first overcoat film and the firstportion of the resin film using the first solvent to remove the resinfilm to the respective first depths in the recesses.
 15. The method ofclaim 14, wherein the TAG-based process comprises: depositing a secondovercoat film on the substrate, the second overcoat film comprising TAG;heating the substrate sufficiently to cause the TAG to generate a secondacid within the second overcoat film and to diffuse the second acid asecond depth into remaining portions of the resin film causing a secondportion of the resin film to become soluble to a second solvent; anddeveloping the second overcoat film and the second portion of the resinfilm using a second solvent resulting in the resin film being recessed apredetermined depth in the recesses defined by the microfabricationstructures.
 16. The method of claim 15, wherein the first solvent andthe second solvent are a same type of solvent.
 17. The method of claim13, wherein performing, using the PAG-based process, the localizedremoval of the resin to remove the resin film to the respective firstdepths in the recesses comprises repeating the PAG-based process atleast twice.
 18. The method of claim 13, wherein meeting thepredetermined condition comprises repeating the TAG-based process apredetermined number of times.
 19. The method of claim 13, whereinrepeatedly performing, using the TAG-based process and until thepredetermined condition is met, the uniform removal of the remainingportion of the resin film comprises performing the TAG-based processonce.
 20. The method of claim 13, wherein meeting the predeterminedcondition comprises removing the resin film to respective predetermineddepths in the recesses leaving respective heights of resin film in therecesses that correspond to respective predetermined heights.
 21. Themethod of claim 13, wherein a concentration of TAG in an overcoat filmis different on a first performance of the TAG-based process than on asubsequent performance of the TAG-based process.